In general, the viscosity of fluid increases as temperature decreases, and decreases as temperature increases. This phenomenon can be explained by decreasing mobility of molecules as temperature decreases. But, we found the opposite phenomenon that viscosity decreases as temperature decreases in particular mixed surfactant system. To analyze this phenomenon, various experiments have been proceeded such as composition (anionic, nonionic, zwitterionic surfactant), variation of zwitterion surfactants, structure of hydrophobic chains, structure of Hydrotrope, variation of pH. Conclusively, controlling the complex of zwitterion and anionic surfactant, we could control the viscosity of mixed surfactant system on variation of temperature. We analyzed this phenomenon theoretically, and then can complete "The technology of viscosity control by temperature in micellar phase".